This research poses a minor increase over minimal risk for subjects enrolled in the intervention group. The anticipated risks include mild dehydration and/or hypoglycemia of neonates in the "physiologic fluid" intervention group. This risk is minor as all newborns in the NICU have urine output recorded every three hours, point-of-care glucose monitoring on admission and at least once every twelve hours thereafter, and serum electrolytes checked between 12 and 24 hours of life. If neonatal dehydration is noted as defined by urine output < 2mL/kg/hour over a twelve hour period, serum sodium < 130 mEq/L or > 150 mEq/L, weight loss of more than 10% of birth weight, or blood glucose by point-of-care testing of < 40 mg/dL, the child will be removed from the study and appropriate fluid resuscitation will be initiated. These guidelines for removal from the study are the same as or more conservative than criteria used for rehydration in clinical care, so long-term adverse sequelae of this level of brief mild dehydration or hypoglycemia are not expected.